I want to use a different default Avatar for those users who post that don't use Gravatar. The default is currently this image

and I want to change it to something else (another image). I have tried changing the

comments-paged.php
legacy.comments.php

files that are pointing to the file no-gravatar.gif to my new file but still no go. Also I have placed the new file in the wp-content/themes/atahualpa332/images folder where the no-gravatar.gif file is and even tried naming the new file to no-gravatar.gif and nothing seems to work. It always seems to use the default image that came with Atahualpa. Users using Gravatars works fine. I am using version 3.3.2. Any help would be appreciated. Thanks